Level 1 router summarization is done only for external routes (redistributed routes from other protocols) because the level 1 router does not receive any routes from the level 2 routers. As such, there is no need to summarize routes from level 2 routers—you can summarize both level 1 and external routes in level 2. External routes can be summarized only at the redistributing router. After the LSP is originated, it cannot be summarized. Summarizing of external ..
Certain traffic types, such as Layer 2 keepalives and Layer 3 routing protocol messages, are absolutely critical to maintaining network stability. Therefore, it is vital to understand how the Cisco IOS Software handles these traffic types, especially when provisioning WAN links that might experience sustained periods of congestion. By default, Cisco IOS Software (in accordance with RFC 791 and RFC 2474) marks Interior Gateway Protocol (IGP) traffic (such as Routing Informati..
Adjusting for Daylight Saving Time
Some areas, such as most of North America and Europe, have consistent and common rules for when to switch between winter or Standard time and summer or Daylight Saving Time. The traditional North American rule, and the default for Cisco routers when they are configured for summer time, is to move an hour ahead at 2:00 AM on the first Sunday in April, and back an hour at 2:00 AM on the last Sunday in October. Router#configure terminal Enter configuration commands, one per li..
Manually Configuring IPv6 Addresses on an Interface
You can configure an IPv6 unicast address on an interface by using a very similar process to how we set up IPv4 addresses in previous chapters of this book: Router1#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router1(config)#ipv6 unicast-routing Router1(config)#interface FastEthernet0/0 Router1(config-if)#ipv6 address AAAA::1/64 Router1(config-if)#exit Router1(config)#end Router1# We can configure an IPv6 Anycast address by using ..
Configuring a PAgP EtherChannel
To configure switch ports for PAgP negotiation (the default), use the following commands: Switch(config)# interface type mod/num Switch(config-if)# channel-protocol pagp Switch(config-if)# channel-group number mode {on | {{auto | desirable} [non-silent]}} On all Cisco IOS–based Catalyst models, you can select between PAgP and LACP as a channel-negotiation protocol. Some older models, however, offer only PAgP, so the channel-protocol command is not available. Each inte..
